How do you not know the voices are real?

As someone with out schizophrenia I always wondered about this. Like, if you don't know and started hearing voices, I get how that's scary. But once you get diagnosed, like, why can't you just go "uh the fake voices are back. Rolls eyes" .

Like, I use to be a Christian and be afraid of magic and curses. But now I found out that it's not real so of somebody was cursing me. I wouldn't care cause it's not real. Why can't you take that approach with hearing voices? Or do you do that already and schizophrenia is just badly portrayed in movies?